“At 31, we’d had all these great years as a band, and then we took time off, and I basically became Mr. Mom [to son Bronx Mowgli, now 6]. I had the beard, the flannel shirt. I didn’t know what my identity was,” he said. “That factored in. When your identity is what you do, it’s hard when you stop doing it.”

Wentz enjoys an afternoon in West Hollywood with son Bronx.INF

He continued, “It was the first time where I was like, ‘Well, no one’s really taking my picture. I’m just basically hanging out with my kid all day. Who cares?’ I think when you stop caring about your personal appearance, your personal hygiene, it makes you even more depressed, but it makes you do it more. It’s like a vicious cycle.”

Wentz, 35, admits that Simpson, whom he was married to from 2008-2011, leaving didn’t exactly improve his outlook.

“I would be an idiot to think that I didn’t contribute to the unraveling of it,” he admitted. “Of course, at first, I’m like, ‘This sucks! You bailed on me!’ But you get perspective. We have a kid together.”

On the bright side, he isn’t jaded.

Wentz welcomed son Saint Lazslo with longtime girlfriend Meagan Camper in August 2014 and says: “I think it’s important to the kids. I do still believe in marriage. My parents are married. My sister is married.”